THI 52 inhibits inducible nitric oxide synthase gene expression in RAW 264.7 cells and rat lung tissue by lipopolysaccharide

Previously we reported that THI 52 inhibits tumor necrosis factor (TNF)-alpha mRNA expression in mouse peritoneal macrophages exposed to LPS plus IFN-gamma. In the present study, the effects of THI 52 on vascular reactivity ex vivo, and iNOS protein expression (rat lung) were investigated in LPS-treated rats. Treatment of THI 52 concentration-dependently reduced not only serum nitrite production but also the expression of iNOS protein in rat lung tissues. Thoracic aorta taken from LPS injected rat for 8 h ex vivo resulted in suppression of vasoconstrictor effects to phenylephrine (PE), which was restored by THI 52 (20 mg/kg) 30 min prior to LPS. When measured iNOS activity, treatment of THI 52 concentration-dependently reduced the enzyme activity in RAW 264.7 cells activated with LPS plus IFN-gamma. Likewise, iNOS activity was significantly reduced in lung tissues taken those rats that were injected THI 52 prior to LPS injection compared with LPS injection alone. These results strongly suggest that THI 52 can suppress iNOS gene expression induced by LPS, and restore the vascular contractility to PE. Thus, THI 52, a new synthetic isoquinoline alkaloid, may be beneficial in inflammatory disorders where production of NO is excessed by iNOS expression.

Inhibition of tumor necrosis factor-alpha mRNA expression by a limited series of tetrahydroisoquinolines in mouse peritoneal macrophages

Tumor necrosis factor-alpha (TNF-alpha) plays important roles in inflammatory responses. Some of tetrahydroisoquinoline (THI) compounds exhibited to inhibit iNOS expression in animal studies and RAW 264.7 cells, but the action of THI on inflammatory reaction was not fully investigated. In the present study, we examined a limited series of THIs (higenamine, YS-51 and THI-52) on the TNF-alpha mRNA expression in mouse peritoneal macrophages by Northern analysis. When thioglycollate-stimulated peritoneal macrophages were incubated with LPS (100 ng/ml), expression of TNF-alpha mRNA was evident and reached its maximum at 2.5 h, which was reduced concentration-dependently by treatment with THIs. When the TNF-alpha activity of macrophage-conditioned media was measured using a TNF-sensitive L929 fibroblast cell line, CCL 1, all THIs increased the cell viability in a concentration dependent manner. The concentrations of THIs used are not cytotoxic by itself when analysed by MTT. Furthermore, nitrite/nitrate level was significantly reduced by the presence of THIs in cells treated with LPS+ interferon-gamma (IFN-gamma). It is concluded, thus, that these results strongly indicated that THIs can suppress the TNF-alpha expression and reduce NO, which may be useful for the inflammatory disorders.